This invention relates to a pipe joint for fitting together synthetic resin pipes in a secure, positive and locking manner.
Heretofore, various kinds of pipe fittings and methods for joining pipes have been developed. There is, for example, a packing type of pipe fitting in which a resilient packing is inserted between the pipes to join them together. In this type of fitting it is necessary to prevent the pipes from slipping apart, since they may otherwise be easily separated again due to their resiliency. In order to obviate this drawback, it is known to provide annular grooves in the inner periphery of the female pipe receiving portion and in the outer periphery of the male pipe insertion portion, and to position a split steel anchor ring in the grooves, as shown in Japanese Patent Publication 6738/64.
However, in such a method, since the metal ring contains a slit, the ring gap may be distorted or bent when the ring widens or narrows its diameter to fit into the annular pipe grooves during assembly, whereby a perfect fit is difficult to obtain. Furthermore, the sharp gap surfaces may bite into the male insertion portion. If the latter is made of a synthetic resin it may thus be easily damaged, or its diameter may become narrow whereby the ring is easily detachable from the pipe. Further, since the ring is made of metal it is easily corroded by the fluids flowing in the pipe, and it is thus almost impossible to use these types of pipe fittings for long periods of time.
In the prior art example shown in FIG. 1, since the stopper ring 4'" fitted into the grooves 7'" and 9'" has a square or rectangular cross section, it may become twisted by the side walls of the grooves and even become detached from the grooves and damaged when a separation force is exerted between the insertion portion 6'" and the receiving portion 3'". Thus, the ring 4'" may not always provide a tight, secure fit, and it is very difficult to use it in actual practice.